Coil for fluid heating furnaces



NOV. 21, 1933. BERGMAN 1,936,284

COIL FOR FLUID HEATING FURNACES Filed March 16, 1951 2 Sheets-Sheet 1 J'WZ/YZ {07 $077016! (113677771072, L:

Nov. 21, 1933. D. J. BERGMAN COIL FOR FLUID HEATING FURNACES Filed March 16, 1931 2 Sheets-Sheet 2 v fizz/evzforr fpoflaZd (117965 Patented Nov. 21, 1933 UNITED STATES PATENT OFFICE COIL FOR FLUID HEATING FURNACES Application March 16, 1931. Serial No. 522,921

2 Claims.

This invention relates to improvements in heating elements and refers particularly to the construction and disposition of fluid conduits within a fluid heating furnace such as an oil cracking furnace or the like.

In a more specific sense the invention has reference to means for heating hydrocarbon oils during their passage through tubular elements, improvements over present methods being disclosed which admit of the application of radiant heat to oil streams in a controllable manner.

It has become quite common practice in the art of the heat treatment of hydrocarbon oils to pump oil streams through a continuous tubular element, a portion of which is so disposed that it receives substantially only radiant heat and the other portions of which receive heat principally by convection from direct contact of hot combustion gases with the tubes, the major portion of the radiant energy produced incidental to the combustion of fuel having been dissipated prior to the direct impingement of the products of combustion upon the tubes. The control of the rate of addition of radiant heat has been effected by disposing tubular elements at definite distances with respect to the source of radiant energy and pumping the oils in a direction and at a rate which prevents the development of excessive temperature differences between the wall of the tube and the oil stream in immediate contact therewith.

A further development of the art has involved the application of the principle of shunt or parallel flow to lessen the pressure head required to pump a given quantity of fluid through heating coils of restricted diameter. It is with improvements in the utilization of radiant heat in elements embodying the principle of parallel flow that the present invention is concerned, novel types of flow being disclosed and novel mechanical means described for connecting succeeding lengths of tubing in such a manner as to render the flow possible.

In the usual method of operating under par-- allel flow conditions, the oil stream entering a tubular element is divided to enter corresponding pipe lengths at the other end of which a commonheader is provided which receives the oil from both tubes and is constructed to again divide the stream entering two succeeding tubes in a reverse direction. In heating oil streams to the temperatures necessary to effect their conversion into products 01' lower boiling point range, the

oils frequently tendto deposit carbon and in such a flow as the one described wherein a re-- division of the stream is eflected at each endconnecting header carbon may and frequently does accumulate to a greater extent in one of two corresponding tube sections than in the other, or deposits may accumulate in the header itself under the conditions of turbulence obtaining therein in such a manner as to divert more of the oil stream through one tube than through the. other. This results in an inequality in the rate of flow in the two tubes and in the development of higher temperatures in the tube receiving the lesser quantity of oil which is undesirable. The sheet of this is cumulative, the oil stream flowing at a slower rate being raised to a higher temperature and thus tending to deposit still more carbon which may eventually completely plug the tube and cause its overheating to a dangerous degree. The present invention combines the advantage of other tube arrangements with respect to distribution of heat and flow of oil under cracking conditions while eliminating or minimizing the disadvantage of the other system in these respects. The advantage of two long parallel coils is that a given amount of stoppage in'one coil has much less efiect upon flow past the stoppage than the same stoppage in one of two short parallel tubes. On the other hand, present methods of paralleling the coils usually result in inequalities in heating because of variations in firing conditions. The present invention discloses a method of end- 35 connecting succeeding parallel tube sections in such manner that this condition cannot occur.

In one specific embodiment the invention comprises dividing an oil stream into substantially equal portions and passing the divided portions without further recombination through substantially equivalent and parallel tubular elements disposed to receive radiant heat. a

The details of an operation comprised within the scope of the invention may be well described by reference to the accompanying drawings which show by diagrammatic and conventional figures forms of apparatus and equipment which may I be employed. I

In the drawings, Fig. 1 is a top plan view of an arrangement of tubular elements designed to receive radiant heat.

Fig. 2 is an end elevational view of the tubes shown in Fig. 1.

Fig. 3 is a detail view of means for end-connecting the straight portions of the tubular element.

Fig. 4 illustrates a side elevational view partly in section 01' the device shown in Fig. 3.

Figs. 5 and 6 show corresponding views of a slightly modified form of return header which may be used.

Referring particularly to Figs. 1 and 2, the numeral 1 indicates a continuous element which may receive one portion of a divided stream of oil and numeral 2 indicates a similar element which may receive the remaining equivalent portion. It will be evident from a consideration of the figures that the streams flow strictly parallel Without recombination at any point and that the tendency for variations in rate of flow in adjacent portions of the two elements is reduced to a minimum.

Referring particularly to Figs. 3 and 4, elements 7 and 8 represent separate end-connections which may be utilized to reverse the direction of flow of corresponding portions of the divided oil stream. These connections may be of a type known as the stream-line type to lessen pressure drop due to turbulence. The joint between the end of the pipe and the end of one of the connections is shown at 11 in Fig. 4, the bearing pressure necessary for making this joint tight being provided by a bolt 12 which turns through bar 10, the ends of said bar being inserted in slots or grooves 20 in a yoke 9 which in turn is held in place on the pipe by rolls 19. Similarly tight joints may be provided at the end of each straight pipe length as required.

Another means of efiecting reversal of flow may be understood by reference to Figs. 5 and 6 which represents a box type of return header provided with channels 14 and 15, the ends of which register with the ends of the straight pipe sections which it is desired to connect.

This header may comprise a fixed member 17, held in place by rolls 21 in the tube, or by welding or other suitable means, as indicated at 2-1 and a corresponding removable member 18 held in place during operation by bolts 16. Members 17 and 18 may each be provided with a portion of channels 14 and 15 as corresponding grooves, which can be cleaned upon removal of member 18.

Other types of end-connecting devices may be employed within the scope of the invention and it is not intended that the ones described in some detail in Figs. 3, 4, 5 and 6 shall be considered in a limiting sense.

I claim as my invention:

1. In a coil adapted for the substantially equal heating of fiuid in a plurality of separate flows, one side of the coil being exposed to a greater degree of heat than the other in a fluid heating furnace, the improvement which comprises, in combination, a plurality of parallelly disposed fluid passageways, means connecting alternate passageways in series to provide a plurality of parallel flows through said passageways, adjacent passageways being disposed in substantially the same plane, andsaid connecting means for alternate passageways being disposed alternately on opposite sides of the plane of the passageways.

2. In a coil adapted for the substantially equal heating of fluid in a plurality of separate flows, one side of the coil being exposed to a greater degree of heat than the other in a fluid heating furnace, the improvement which comprises, in combination, a plurality of parallelly disposed fluid passageways, removable headers connecting alternate passageways in series to provide a plurality of parallel flows through said passageways, adjacent passageways being disposed in substantially the same plane, and said headers for alternate passageways being disposed alternately on opposite sides of the plane of the passageways.

DONALD J. BERGMAN. 

